Breast Cancer Drug Exceeds Study's Goal

March 31, 2005 -- Early results from a study of the breast cancer drug Herceptin were so positive that the researchers stopped the study early.

Herceptin (trastuzumab) is an antibody that targets cancer cells that make too much of a protein called HER-2/neu. It attaches to cells that have the HER-2/neu protein, which is known to stimulate cell growth and prevent breast cancer cell death. That accounts for about 25%-30% of all breast cancers, say the researchers.

Approved by the FDA in 1998, Herceptin isn't a cure, and it's not without drawbacks. When Herceptin binds to these breast cancer cells it can prevent the spread of breast cancer. However rare side effects can include heart muscle damage, which can lead to heart failure.

The small study -- which was sponsored by the makers of the drugs used (including Herceptin) --doesn't gauge long-term survival. Instead, it's a window on early outcome after treatment.

Still, the data led the researchers to stop what they were doing, regroup, and give new participants the option to try Herceptin.

Trying a New Tactic

The doctors, based at the University of Texas M.D. Anderson Cancer Center, took a new approach with Herceptin.

Instead of using Herceptin with chemotherapy after breast cancer surgery, they reversed that order, treating women with Herceptin and chemotherapy before surgery.

Participants were 42 women with HER-2/neu positive breast cancer. All had early stages of the breast cancer (cancer confined to the breast) and were candidates for lumpectomy (breast-conserving surgery) or mastectomy (breast removal). The women were 48-52 years old, on average.

Each woman got four cycles of chemotherapy. The researchers assigned 23 of the patients to also get Herceptin along with chemo.

Originally, the researchers wanted to see if Herceptin, given before surgery, would reduce evidence of breast cancer after treatment. The response rate after treatment is a marker for long-term survival. In this study the researchers hoped to see a 20% improvement in the response rate in women receiving both drugs.

The response rate was 67% in the Herceptin-plus-chemotherapy group. The rate was 26% for those who got chemotherapy alone.

None of the women developed heart failure, a possible side effect of Herceptin.

Seeing that, the researchers stopped the study. They had planned to enroll more women, but they decided to make Herceptin available to all future participants, instead of leaving some without the drug.

About half of the women had estrogen-sensitive tumors. That didn't affect the findings, say researcher Aman Buzdar, MD, and colleagues.